Information apparatuses storing therein important information such as personal information have been wide spread in recent years. Examples of such information apparatuses include mobile telephone sets and personal computers each storing personal information such as a telephone number and a mail address, and authentication apparatus and entry/exit management apparatuses each storing biometrix information such as a fingerprint pattern and an iris pattern and authentication information such as a password to conduct personal authentication.
It is a critical problem in such an information apparatus how to prevent wrong deeds (hereinafter “tampering”) by a party who attempts to illegally acquire stored information by breaking open a cover and a housing of the information apparatus and taking out a storage device storing the information from the information apparatus or by removing the information apparatus together with the housing from a wall surface. Various technologies have therefore been proposed to solve this problem.
One of such technologies proposes a construction of a housing for storing an electronic appliance in which a cover is provided to a housing, screws for fitting the housing to a wall surface cannot be handled unless the cover is open, and the cover and the housing are fixed to each other through the screws so that the housing cannot be removed from the wall surface (for example, refer to Japanese Patent No. 2,781,127).
Another construction for detecting opening/closing of a cover of an information apparatus by use of a light reception/emission portion comprising a pair of light reception portion and a light emission portion has been proposed, too (for example, refer to JP-A-5-325751). In this information apparatus, the light reception portion is formed on the housing side and a light shading protuberance is formed on the cover side in such a fashion as to cut off an optical path of the light reception/emission portion when the cover is closed. The optical path is opened when the cover is opened, the light reception portion detects the rays of light from the light emission portion, the output of the light reception/emission portion is turned ON and an abnormality signal is generated.
In the information apparatus disclosed in Japanese Patent No. 2,781,127, however, the illegal party can easily remove the information apparatus from the housing by first forcing the cover to open, finding out the screw holes for fixing the housing and thereafter removing the housing.
The information apparatus disclosed in JP-A-5-325751 can detect tampering such as breaking of the cover and can then generate the abnormality signal, it is true, but when tampering is made in such a fashion that the information apparatus itself is removed from the wall surface and taken away, the information apparatus cannot at all detect such tampering.